An acoustic wave device may be provided in wireless communication devices, which may typically be portable phones. The acoustic wave device has an acoustic wave element formed on a piezoelectric substrate. The acoustic wave device has a function area in which an acoustic wave is excited by the acoustic wave element. Such a function area may include an interdigital transducer (IDT). An opening is defined above the function area because the acoustic wave is excited.
An acoustic wave device utilizing a wafer-level packaging scheme directed to downsizing is described in Japanese Laid-Open Patent Publication No. 2006-324894. FIG. 1 of this publication describes the following acoustic wave device. A piezoelectric substrate 100 has a function area (comb electrodes 110), which is sealed with a resin part (composed of a cavity forming layer 210 and a seal region 230) so as to define a cavity 320 above the function area. An electrode pad (pad electrode 120) electrically connected to the acoustic wave element is formed on the piezoelectric substrate. An opening is formed in the resin part above the electrode pad. The opening is full of a metal layer (electrically conductive via 430). An external circuit may be connected to the acoustic wave element via the metal layer and the electrode pad.